/*
 * Copyright 2002-2013 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.security.web.util.matcher;

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Set;

import javax.servlet.http.HttpServletRequest;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.http.MediaType;
import org.springframework.security.web.util.matcher.RequestMatcher;
import org.springframework.util.Assert;
import org.springframework.web.HttpMediaTypeNotAcceptableException;
import org.springframework.web.accept.ContentNegotiationStrategy;
import org.springframework.web.context.request.ServletWebRequest;

/**
 * Allows matching {@link HttpServletRequest} based upon the {@link MediaType}'s
 * resolved from a {@link ContentNegotiationStrategy}.
 *
 * By default, the matching process will perform the following:
 *
 * <ul>
 * <li>The {@link ContentNegotiationStrategy} will resolve the {@link MediaType}
 * 's for the current request</li>
 * <li>Each matchingMediaTypes that was passed into the constructor will be
 * compared against the {@link MediaType} instances resolved from the
 * {@link ContentNegotiationStrategy}.</li>
 * <li>If one of the matchingMediaTypes is compatible with one of the resolved
 * {@link MediaType} returned from the {@link ContentNegotiationStrategy}, then
 * it returns true</li>
 * </ul>
 *
 * For example, consider the following example
 *
 * <pre>
 * GET /
 * Accept: application/json
 *
 * ContentNegotiationStrategy negotiationStrategy = new HeaderContentNegotiationStrategy()
 * MediaTypeRequestMatcher matcher = new MediaTypeRequestMatcher(negotiationStrategy, MediaType.APPLICATION_JSON);
 * assert matcher.matches(request) == true // returns true
 * </pre>
 *
 * The following will also return true
 *
 * <pre>
 * GET /
 * Accept: *&#47;*
 *
 * ContentNegotiationStrategy negotiationStrategy = new HeaderContentNegotiationStrategy()
 * MediaTypeRequestMatcher matcher = new MediaTypeRequestMatcher(negotiationStrategy, MediaType.APPLICATION_JSON);
 * assert matcher.matches(request) == true // returns true
 * </pre>
 *
 * <h3>Ignoring Media Types</h3>
 *
 * Sometimes you may want to ignore certain types of media types. For example,
 * you may want to match on "application/json" but ignore "*&#47;" sent by a web
 * browser.
 *
 * <pre>
 * GET /
 * Accept: *&#47;*
 *
 * ContentNegotiationStrategy negotiationStrategy = new HeaderContentNegotiationStrategy()
 * MediaTypeRequestMatcher matcher = new MediaTypeRequestMatcher(negotiationStrategy, MediaType.APPLICATION_JSON);
 * matcher.setIgnoredMediaTypes(Collections.singleton(MediaType.ALL));
 * assert matcher.matches(request) == false // returns false
 * </pre>
 *
 * <pre>
 * GET /
 * Accept: application/json
 *
 * ContentNegotiationStrategy negotiationStrategy = new HeaderContentNegotiationStrategy()
 * MediaTypeRequestMatcher matcher = new MediaTypeRequestMatcher(negotiationStrategy, MediaType.APPLICATION_JSON);
 * matcher.setIgnoredMediaTypes(Collections.singleton(MediaType.ALL));
 * assert matcher.matches(request) == true // returns true
 * </pre>
 *
 * <h3>Exact media type comparison</h3>
 *
 * By default as long as the {@link MediaType} discovered by
 * {@link ContentNegotiationStrategy} returns true for
 * {@link MediaType#isCompatibleWith(MediaType)} on the matchingMediaTypes, the
 * result of the match is true. However, sometimes you may want to perform an
 * exact match. This can be done with the following examples:
 *
 * <pre>
 * GET /
 * Accept: application/json
 *
 * ContentNegotiationStrategy negotiationStrategy = new HeaderContentNegotiationStrategy()
 * MediaTypeRequestMatcher matcher = new MediaTypeRequestMatcher(negotiationStrategy, MediaType.APPLICATION_JSON);
 * matcher.setUseEquals(true);
 * assert matcher.matches(request) == true // returns true
 * </pre>
 *
 * <pre>
 * GET /
 * Accept: application/*
 *
 * ContentNegotiationStrategy negotiationStrategy = new HeaderContentNegotiationStrategy()
 * MediaTypeRequestMatcher matcher = new MediaTypeRequestMatcher(negotiationStrategy, MediaType.APPLICATION_JSON);
 * matcher.setUseEquals(true);
 * assert matcher.matches(request) == false // returns false
 * </pre>
 *
 * <pre>
 * GET /
 * Accept: *&#47;*
 *
 * ContentNegotiationStrategy negotiationStrategy = new HeaderContentNegotiationStrategy()
 * MediaTypeRequestMatcher matcher = new MediaTypeRequestMatcher(negotiationStrategy, MediaType.APPLICATION_JSON);
 * matcher.setUseEquals(true);
 * assert matcher.matches(request) == false // returns false
 * </pre>
 *
 * @author Rob Winch
 * @since 3.2
 */

public final class MediaTypeRequestMatcher implements RequestMatcher {
    private final Log logger = LogFactory.getLog(getClass());
    private final ContentNegotiationStrategy contentNegotiationStrategy;
    private final Collection<MediaType> matchingMediaTypes;
    private boolean useEquals;
    private Set<MediaType> ignoredMediaTypes = Collections.emptySet();

    /**
     * Creates an instance
     * @param contentNegotiationStrategy the {@link ContentNegotiationStrategy} to use
     * @param matchingMediaTypes the {@link MediaType} that will make the {@link RequestMatcher} return true
     */
    public MediaTypeRequestMatcher(ContentNegotiationStrategy contentNegotiationStrategy, MediaType... matchingMediaTypes) {
        this(contentNegotiationStrategy, Arrays.asList(matchingMediaTypes));
    }

    /**
     * Creates an instance
     * @param contentNegotiationStrategy the {@link ContentNegotiationStrategy} to use
     * @param matchingMediaTypes the {@link MediaType} that will make the {@link RequestMatcher} return true
     */
    public MediaTypeRequestMatcher(ContentNegotiationStrategy contentNegotiationStrategy, Collection<MediaType> matchingMediaTypes) {
        Assert.notNull(contentNegotiationStrategy, "ContentNegotiationStrategy cannot be null");
        Assert.notEmpty(matchingMediaTypes, "matchingMediaTypes cannot be null or empty");
        this.contentNegotiationStrategy = contentNegotiationStrategy;
        this.matchingMediaTypes = matchingMediaTypes;
    }

    public boolean matches(HttpServletRequest request) {
        List<MediaType> httpRequestMediaTypes;
        try {
            httpRequestMediaTypes = contentNegotiationStrategy.resolveMediaTypes(new ServletWebRequest(request));
        }
        catch (HttpMediaTypeNotAcceptableException e) {
            logger.debug("Failed to parse MediaTypes, returning false", e);
            return false;
        }
        if(logger.isDebugEnabled()) {
            logger.debug("httpRequestMediaTypes=" + httpRequestMediaTypes);
        }
        for(MediaType httpRequestMediaType : httpRequestMediaTypes) {
            if(logger.isDebugEnabled()) {
                logger.debug("Processing " + httpRequestMediaType);
            }
            if(shouldIgnore(httpRequestMediaType)) {
                logger.debug("Ignoring");
                continue;
            }
            if(useEquals) {
                boolean isEqualTo = matchingMediaTypes.contains(httpRequestMediaType);
                logger.debug("isEqualTo " + isEqualTo);
                return isEqualTo;
            }
            for(MediaType matchingMediaType : matchingMediaTypes) {
                boolean isCompatibleWith = matchingMediaType.isCompatibleWith(httpRequestMediaType);
                if(logger.isDebugEnabled()) {
                    logger.debug(matchingMediaType + " .isCompatibleWith " + httpRequestMediaType + " = " + isCompatibleWith);
                }
                if(isCompatibleWith) {
                    return true;
                }
            }
        }
        logger.debug("Did not match any media types");
        return false;
    }

    private boolean shouldIgnore(MediaType httpRequestMediaType) {
        for(MediaType ignoredMediaType : ignoredMediaTypes) {
            if(httpRequestMediaType.includes(ignoredMediaType)) {
                return true;
            }
        }
        return false;
    }

    /**
     * If set to true, matches on exact {@link MediaType}, else uses
     * {@link MediaType#isCompatibleWith(MediaType)}.
     *
     * @param useEquals
     *            specify if equals comparison should be used.
     */
    public void setUseEquals(boolean useEquals) {
        this.useEquals = useEquals;
    }

    /**
     * Set the {@link MediaType} to ignore from the
     * {@link ContentNegotiationStrategy}. This is useful if for example, you
     * want to match on {@link MediaType#APPLICATION_JSON} but want to ignore
     * {@link MediaType#ALL}.
     *
     * @param ignoredMediaTypes
     *            the {@link MediaType}'s to ignore from the
     *            {@link ContentNegotiationStrategy}
     */
    public void setIgnoredMediaTypes(Set<MediaType> ignoredMediaTypes) {
        this.ignoredMediaTypes = ignoredMediaTypes;
    }

    @Override
    public String toString() {
        return "MediaTypeRequestMatcher [contentNegotiationStrategy="
                + contentNegotiationStrategy + ", matchingMediaTypes="
                + matchingMediaTypes + ", useEquals=" + useEquals
                + ", ignoredMediaTypes=" + ignoredMediaTypes + "]";
    }
}